Doctor blade pressure/angle adjusting mechanism

ABSTRACT

This disclosure relates to a novel method of and means for automatically and repetitiously increasing and decreasing doctor blade/cylinder contact pressure and doctor blade/cylinder angle to lessen or prevent &#39;&#39;&#39;&#39;coverage&#39;&#39;&#39;&#39;, i.e., the presence of ink haze in the nonimage area of a print.

States atet n 1 Trant et al.

[ 1 May 1, 1973 DOCTOR BLADE PRESSURE/ANGLE ADJUSTING MECHANISM [75] Inventors: Robert F. Trant, Chicago; Kenneth W. Gray, Justice; John W. Capt-0n, Palos Heights, all of 111.

[73] Assignee: Continental Can Company, 1nc.,

New York, NY.

[22] Filed: Feb. 1, 1971 [21] Appl. No.: 111,201

[52] US. Cl ..101/169, 101/170 [51] Int. Cl. ..B41f 9/10 [58] Field of Search ..l01/157, 169, 170,

[56] References Cited UNITED STATES PATENTS Wood ..l01/l69 2,550,454 4/1951 Crafts et a]. ..l01/157 2,644,395 7/1953 Reyrebrune et al. ....10l/l57 3,389,655 6/1968 Lorenz et al. ..l01/l57 Primary Examiner-J. Reed Fisher Attorney-Diner, Brown, Ramik & Holt [57] ABSTRACT This disclosure relates to a novel method of and means for automatically and repetitiously increasing and decreasing doctor blade/cylinder contact pressure and doctor blade/cylinder angle to lessen or prevent coverage, i.e., the presence of ink haze in the nonimage area of a print.

6 Claims, 3 Drawing Figures Patented May 1, 1973 2 Sheets-Sheet 1 S m T w T NM m N PRO Q E RGR D V T .D- 4 m n m m H ma mu B H D G QK i115 ra Patented May 1, 1973 2 Sheets-Sheet 2 \NVENTURS RDBEQT F. 'YRQNT, .ILENNETH w. GRQYCn JDHN wcaprzcm DOCTOR BLADE PRESSURE/ANGLE ADJUSTING MECHANISM The problem of coverage, also variously known as fogging, hazing, shadowing, etc., is most peculiar to gravure printing, and this defect contributes significantly to printed material being rejected because of poor quality. This occurs because of the presence of ink on, for example, nonengraved non-printing portions of an engraved cylinder of a typical rotary gravure printing press. The quantity of the ink or other printing medium on the engraved cylinder is regulated by a doctor blade which reciprocates in a direction parallel to the axis of cylinder rotation with both the angle of the doctor blade and the amount of pressure exerted thereby against the cylinder being manually adjustable. Ordinarily the operator of the printing press will notice coverage or hazing developing and through experience adjust the doctor blade pressure and/or angle which will usually correct the situation fora period of time but coverage again will reoccur either at the same or a different place on the cylinder roll and further manual adjustments are thus continuously required.

In keeping with the present invention a novel object thereof is to provide an automatic system for varying the pressure of the doctor blade against the cylinder in the manner that substantially eliminates the problem of coverage, and simultaneously automatically varying the doctor blade/cylinder angle.

The foregoing object is achieved by a gear train coupled to the normally reciprocating doctor blade with a worm wheel of the gear train being automatically rotated clockwise and counterclockwise during the reciprocation of the doctor blade to automatically and repetitiously increase and decrease doctor blade/cylinder contact pressure and doctor blade cylinder angle in a reciprocal manner whereby hazing or coverage is eliminated for an indefinite period of time.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claimed subject matter, and the several views illustrated in the accompanying drawings.

IN THE DRAWINGS FIG. 1 is a fragmentary top plan view ofa novel doctor blade mechanism constructed in accordance with this invention, and illustrates a doctor blade carried by a reciprocal carriage and means between a frame of the machine and a worm for automatically and repetitiously increasing and decreasing doctor blade/cylinder contact pressure and angle.

FIG. 2 is a fragmentary side view of the doctor blade mechanism of FIG. I, and more clearly illustrates the Ink applied to the gravure cylinder is doctored from the nonengraved or land areas of the cylinder and is transferred to the web or sheet from the engraved or etched areas of the cylinder. If the doctor blade does not remove ink from the non-engraved or land areas of the cylinder, this ink is transferred to the corresponding areas of the web or sheet of material being printed and appears thereon as coverage, fogging, hazing, shadowing, etc. which is highly undesirable resulting in poor quality printing and the rejection of printed material. It has been discovered that by automatically increasing and decreasing doctor blade/cylinder contact pressure and doctor blade/cylinder angle a gravure printing or analogous operations can be run almost indefinitely without experiencing the aforementioned coverage, hazing, shadowing, etc., problems.

In keeping with the foregoing the present invention provides a novel doctor blade mechanism generally designated by the reference numeral 10 which is associated with a gravure printing press 11 having side frames 12, 13 in which is conventionally journalled for rotation an engraved cylinder 14 having a surface 15 which includes both printing and non-printing areas upon which is deposited ink or similar printing medium by conventional means (not shown). The cylinder 14 is rotated by suitable gearing (not shown) past the doctor blade mechanism 10 and more specifically past a doctor blade 16 engaging the surface 15 in the manner best illustrated in FIG. 3.

The doctor blade 16 is clamped between a pair of bars 17, 18 (FIG. 3) of a doctor blade holder 20 which is part of a reciprocal doctor blade carriage 21. The doctor blade carriage 21 is pivotally mounted upon a shaft 22 by means of a bore 23 with axially opposite ends of the shaft 22 being fixed in brackets 24, 25. A cylindrical shaft 26 also forms a portion of the reciprocal carriage 21 and is threaded or otherwise secured to the brackets 24, which in turn include upper and lower guide grooves 27, 28 and 30, 31, respectively.

Rollers 32, 33 are'received in respective guide grooves 27, 28 and are journalled for rotation on respective shafts 34, 35 carried by a sliding block 36 housed within the side frame 13. An adjusting screw 37 is threaded in a bore 38 of the side frame 13 and its terminal end is freely rotatable within the block 36. Thus, upon rotation of a knurled handle 40 the block 36 can be moved up or down for adjusting the doctor blade 16 relative to the surface 15 of the cylinder 14.

The opposite side of the doctor blade mechanism 10 likewise includes guide rollers 41, 42 received in the respective grooves 30, 31 and journalled for rotation .upon respective shafts 43, 44 carried by another slide block 45 in the side frame 12. A like screw 46 threaded in an aperture 47 and having a knurled head 48 is rotated to move the block 45 and thus the guides 41, 42 upward or downward as necessary to adjust the position of the doctor blade 16 relative to the cylinder sur' face 15 in conjunction with a like adjustment performed by the screw 37.

The carriage 21 and thus the doctor blade 16 carried thereby is continuously reciprocated across the surface 15 generally parallel to the axis of the cylinder 14 by a crank 50 having an eccentric 51 pivotally secured to the crank arm 52 which is in turn connected by a pivot pin 53 to the bracket 25. A conventionaldrive motor 54 imparts continuous rotation to the eccentric 51 through a drive chain or pulley 55 thereby continually reciprocating the carriage 21 and the doctor blade 16 carried thereby.

Means for automatically and repetitiously increasing and decreasing the pressure exerted by the doctor blade 16 against the surface of the cylinder 14, as well as the angle between the doctor blade 16 and the surface 15, is generally designated by the reference numeral 60 and includes a gear segment 61 in mesh with a wheel or gear 62 which is in turn in mesh with a worm 63. The gear segment 61 is suitably secured to the carriage 21 while the gear or wheel 62 is mounted for rotation about the shaft 26. The worm 63 is suitably journalled fo r rotation in a frame 64 having a pair of apertured arms 65, 66 through which pass the shaft 26, as is best illustrated in FIG. 2. An exposed enlarged head 67 of the worm 63 is apertured at 68 and an end portion 70 ofa rod 71 is received therein, as best shown in FIG. 3. The opposite end 72 of the rod 71 is threaded and passes through an aperture 73 of a plate 74 welded to the side frame 12. A pair of lock nuts 75, 76 are threaded upon the threaded end portion of the rod 71 on opposite sides of the plate 74.

During the reciprocal movement of the carriage 21 the means 60 is reciprocated therewith and for the major portion of each forward and return stroke of the carriage 21, the gear segment 61, the wheel 62 and the worm 63 are motionless. However, just prior to the end of each stroke the nuts 75 or 76 contact the plate 74 preventing movement of the rod 71 which in turn imparts rotation to the worm 63 which through the wheel 62 and the gear segment 61 increases or decreases the pressure exerted by the doctor blade 16 against the surface 15 of the cylinder 14 as well as a change in the relative angle therebetween. Thus, so long as the end portion 72 of the rod 71 is free to slide within the bore 73 the doctor blade pressure and the angle thereof relative to the surface 15 remains unchanged and would, for example, correspond to the initial pressure and angle set by the rotation of the screws 37, 46. However, when the nuts 75 are positioned upon the threaded end portions 72 to contact the plate 74 upon left-to-right motion of the carriage 21 the worm 63 will rotate clockwise to effect a decrease in pressure and a corresponding decrease in blade angle, while opposite or right-to-left motion resulting in the contact of the nuts 76 against the plate 74 causes an increase in the doctor blade pressure against the surface 15 and an increase in the relative angle therebetween. In this manner the means 60 automatically, repetitiously and cyclically increases and decreases the doctor blade/cylinder contact pressure and angle which has been found to lessen or prevent coverage, haze, etc. for an unlimited time.

While preferred forms and arrangements of parts have been shown in illustrating the invention, it is to be clearly understood that various changes in details and arrangement of parts may be made without departing from the spirit and scope of this disclosure.

We claim:

1. In a doctor blade mechanism including a doctor blade in contact with a surface of a rotating cylinder and means for reciprocating the doctor blade generally transverse to the direction of cylinder rotation, the improvement comprising means operative in response to the transverse reciprocation of said doctor blade for automatically and repetitiously increasing and decreasing doctor blade-cylinder contact pressure thereby les- 5. A method of lessening or preventing coverage comprising the steps of placing a doctor blade in contact with a surface of a rotating cylinder, reciprocating the doctor blade generally transverse to the direction of cylinder rotation, and automatically and repetitiously increasing and decreasing doctor blade-cylinder contact pressure in response to the transverse reciprocation of the doctor blade thereby lessening or preventing coverage.

6. The method as defined in claim 5 including the step of increasing and lessening thedoctor bladecylinder contact pressure during each reciprocal cycle of the doctor blade. 

1. In a doctor blade mechanism including a doctor blade in contact with a surface of a rotating cylinder and means for reciprocating the doctor blade generally transverse to the direction of cylinder rotation, the improvement comprising means operative in response to the transverse reciprocation of said doctor blade for automatically and repetitiously increasing and decreasing doctor blade-cylinder contact pressure thereby lessening or preventing coverage.
 2. The combination as defined in claim 1 wherein said last-mentioned means is operative in response to the transverse reciprocation of said doctor blade and during each reciprocal cycle of said doctor blade.
 3. The combination as defined in claim 1 including means for selectively setting at least the highest doctor blade-cylinder contact pressure.
 4. The combination as defined in claim 1 including means for selectively setting at least the lowest doctor blade cylinder contact pressure.
 5. A method of lessening or preventing coverage comprising the steps of placing a doctor blade in contact with a surface of a rotating cylinder, reciprocating the doctor blade generally transverse to the direction of cylinder rotation, and automatically and repetitiously iNcreasing and decreasing doctor blade-cylinder contact pressure in response to the transverse reciprocation of the doctor blade thereby lessening or preventing coverage.
 6. The method as defined in claim 5 including the step of increasing and lessening the doctor blade-cylinder contact pressure during each reciprocal cycle of the doctor blade. 